Ligia Toro, Ph.D.
Professor
Department of Anesthesiology
University of California, Los Angeles
Division of Molecular Medicine
BH-509A CHS, Box
957115
Los Angeles, CA
90095-7115
E-mail: ltoro@ucla.edu
Tel: 310-794-7809
1980 Master in Sciences in Experimental Biology, Biochemistry specialty,
Universidad Autonoma Metropolitana-I. Mexico, D.F.
1986 Ph.D. in Physiology and Biophysics, Centro de Investigacion y de Estudios
Avanzados del IPN. Mexico, D.F.
2000-Present Professor, Department of Anesthesiology, David Geffen School of Medicine at
UCLA
2000-Present Professor, Department of Molecular & Medical Pharmacology, David Geffen
School of Medicine at UCLA
The laboratory has four main projects: 1) Cardiovascular Biology and Aging with emphasis in coronary and cerebral arteries, 2) Src tyrosine kinases signaling complexes and vascular tone in vessels subject to thrombotic episodes, 3) Molecular Genetics and Cell Biology of Ion channels with focus on voltage and Ca-activated K channels, and 4) Remodeling of Cardiac and Smooth Muscle K channels by Sex Hormones during pregnancy and during functional cardiac hypertrophy. Our studies are focused mainly to understand the molecular, cellular and genetic mechanisms underlying the regulation of cardiovascular K channel remodeling that occurs during aging and under the influence of sex hormones. The activity of this type of ion channels defines smooth muscle tone and cardiac contractility, and thereby, they have a key role on the control of blood pressure, and cardiac function. Our studies will provide tools for Molecular Medicine and will help understand and treat cardiovascular disease in the growing aging population.
c-Src in vascular smooth muscle
Cardiovascular Biology and Aging. We discovered that Ca-activated K (MaxiK) channels are diminished in the coronary arteries of aging rats and humans. A diminution of the relaxing force driven by MaxiK channel activity leads to increased tone with aging. This finding explains why coronary arteries are more prone to spasm with advanced age, and identify MaxiK channels as a therapeutic target to alleviate coronary dysfunction in the elderly. Our studies involve a multidisciplinary approach using molecular, biochemical, immunochemical, pharmacomechanical and electrophysiological approaches. Goals are to: a) identify the subunits involved in MaxiK channel diminished activity, b) investigate if transcriptional regulation is as a mechanism of downregulation, c) determine if similar changes occur in cerebral arteries (resistance) or aorta (conduit), d) investigate if mechanisms of regulation (e.g. c-Src tyrosine kinase pathway involved in proliferation and cell migration) by vasoactive substances are altered during aging, and e) analysis of young vs. old aorta and cardiac transcriptomes using microarray analysis to determine which ion channels or regulatory pathways are greatly altered during aging. Funding, NIH HL47382.
Src tyrosine kinases signaling complexes and vascular tone. This is a new line of investigation that had its origins in our studies of the role of MaxiK channels in vasoconstriction. We recently discovered that Src tyrosine kinases control 5-HT- AngII- and Phenylephrine (Phe)-induced contraction via MaxiK channel inhibition in human coronary arteries and rat aorta. Thus, Src tyrosine kinases (classical regulators of cell migration and differentiation) are emerging as new signals in vascular contraction. Initial experiments indicate that Src tyrosine kinases are primary steps in 5-HT and thromoboxane A2 but not in Phe contractions indicating a selective functional association among receptors, Src tyrosine kinases, and downstream contractile signals. At present we are identifying the molecular complexes, sites of interaction and their selective distribution in specialized cellular domains. The elucidation of primary steps involved in 5-HT and TXA2 smooth muscle stimulation should help in the design of new therapeutic ways to control thrombotic episodes triggered by 5-HT and thromboxane A2. Funding, NIH HL77705.
K channel molecular genetics, cell biology and trafficking. We have cloned a and b1-b4 subunits of human MaxiK channels, and established basic concepts about their topology, gene structure, function-structure relationships, trafficking and polarized targeting. We demonstrated that MaxiK channels distribute to lipid rafts and do not need glygosylation for apical sorting; and discovered a new splice variant that acts as dominant negative regulator of channel expression. We are now investigating if this splice insert is a new retention signal. We have obtained a b1 subunit knockout which is known to be hypertensive demonstrating the role of MaxiK channels in vascular function. Our goals are to: a) determine retention and targeting sequences of MaxiK channels and the role of splice variants, b) obtain a conditional a subunit knockout to determine function of MaxiK channels in a defined spatiotemporal way, c) determine the role of b1 subunit in non-genomic vasorelaxation by estrogen using the b1 knockout, d) investigate colocalization and protein-protein interactions of MaxiK channels with second messengers systems, specially c-Src tyrosine kinase pathway and their subcellular distribution in caveolae, and e) define dynamic changes that occur during gating and conduction using fluorescent labeling. Funding, NIH HL54970
Remodeling of Cardiac and Smooth muscle K channels by sex hormones. We have chosen as a starting model the myometrium that is characterized by huge and rapid changes under the control of sex hormones. We have demonstrated that estrogen regulates Kv4.3 expression during pregnancy using a transcriptional mechanism. Recently, we have expanded our studies to investigate ion channel remodeling during functional cardiac hypertrophy in pregnancy. During pregnancy, the heart undergoes hypertrophy practically doubling its size; this hypertrophy, however, does not lead to heart failure but the heart recovers after partum. Thus, our main goal is to discover the genes that are responsible for the reversibility of hypertrophy or the genes that protect the heart from failure. Special attention will be given to oncogenes like c-Src that mark the initiation of hypertrophy, ion channels that regulate excitability of the cells, and "protective" genes like estrogen receptors or enzymes for estrogen production. We have found that cardiomyocytes may possess a plasma membrane estrogen receptor which could mediate fast regulatory responses. In fact, we found that Kv4.3 channel activity is modulated by estrogen, and by c-Src activity via acute and long-term actions. Acute actions may need plasma membrane receptor and long-term actions may occur through the traditional nuclear receptor. Using high resolution confocal microscopy, microchips, molecular, biochemical and electrical tools, our goals are to: 1) Determine the sex hormones involved in the remodeling of K channel expression in the uterus during pregnancy, 2) Analyze the transcriptome of heart and aorta in non-pregnant, pregnant, and post-partum to discover the genes that trigger cardiac hypertrophy and its reversal during pregnancy, 3) Investigate genomic and non-genomic actions of b-estradiol on K+ channels of cardiac ventriculocytes, especially Kv4.3, 4) Determine the intracellular pathways (e.g. c-Src tyrosine kinase) leading to remodeling of K+ channel gene expression, 5) Analyze colocalization and potential protein-protein interactions of cardiac K+ channels with regulatory signaling pathways/scaffolding proteins (estrogen receptors, c-Src, caveolin). Funding, NIH, HD38983 and NIH, HL071824.
1999-2005 R01 HL47382. NIH. MaxiK channels in aging coronary smooth muscle. PI.
2000-2005 R01 HL54970. NIH. Molecular and functional studies of MaxiK channels. PI.
2004-2008 R01 HL77705. NIH. New roles of Src tyrosine kinases in vascular tone. PI.
2004-2009 R01 HD046510. NIH. K channel and c-Src signaling complexes in smooth muscle. CoPI.
2002-2007 R01 HL071824. NIH. Molecular pathways of heart K channel regulation. Co-PI.
2001-2005 R01 HD38983. NIH. Hormonal regulation of ion channels in myometrium. Co-PI.
1. Alioua A., Mahajan A., Nishimaru K., Zarei M. M., Stefani E., and Toro L. Coupling of c-Src to Large Conductance Voltage- and Ca2+-activated K+ channels as a New Mechanism of Agonist-Induced Vasoconstriction. Proc. Natl. Acad. Sci. USA. 99(22):14560-14565, 2002.
2. Eghbali M., Toro L. and Stefani E. Diminished Surface Clustering and Increased Perinuclear Accumulation of Large Conductance Ca2+-Activated K+ Channel in Mouse Myometrium with Pregnancy. J. Biol. Chem. 278(46):45311-453117, 2003.
3. Kazuhide Nishimaru, Mansoureh Eghbali, Rong Lu, Jure Marijic, Enrico Stefani and Ligia Toro. Functional and Molecular Evidence of MaxiK Channel β1 Subunit Decrease with Coronary Artery Ageing in the Rat. J. Physiol. London. 559(3):849–862, 2004.
4. Masoud M. Zarei, Mansoureh Eghbali, Abderrahmane Alioua, Min Song, Hans-Günther Knaus, Enrico Stefani, and Ligia Toro. An Endoplasmic Reticulum Trafficking Signal Prevents Surface Expression of a Voltage and Ca2+-activated K+ Channel Splice Variant. Proc. Natl. Acad. Sci. USA. 101(27):10072-10077, 2004.
List
of Publications
Others in the Basic Science Research Group
Last updated
02/01/05
E-mail to: ltoro@ucla.edu